Primary frequency standards are atomic clocks that do not need calibration and can run autonomously for long periods of time with minimal time loss. One such atomic clock utilizes an expanding cloud of laser cooled atoms of an alkali metal such as cesium (Cs) or rubidium (“Rb”) in the non-electronic portion of the atomic clock. The non-electronic portion of an atomic clock is sometimes referred to as the physics package. Usually these primary frequency standards and the corresponding physics packages are large and consume a lot of power. While some progress has been made in reducing the size and power consumption of primary frequency standards and their physics packages, further such reductions have been difficult to achieve for both military and civilian applications.